Chert

Pseudotachylite

Chert and Pseudotachylite

Chert

Pseudotachylite

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Definition

Chert is a hard, dark, opaque sedimentary rock which is composed of silica with an amorphous fine-grained texture

Very fine grained fault rock which is composed of glassy matrix that often contains inclusions of wall-rock fragments.

History

Origin

USA

Discoverer

Unknown

Etymology

From flint-like quartz, 1670s, of unknown origin- a local term, which has been taken into geological use

From pseudo- +‎ tachylite, a glassy rock generated by frictional heat within faults.

Class

Sedimentary Rocks

Metamorphic Rocks

Sub-Class

Durable Rock, Hard Rock

Family

Group

Other Categories

Fine Grained Rock, Opaque Rock

Texture

Banded, Rough

Quench

Color

Black, Brown, Green, Grey, Red, White

Black, Brown, Green, Grey, Pink, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Glassy or Pearly

Dull and Soft

Uses

Architecture

Interior Uses

Decorative Aggregates, Homes

Decorative Aggregates, Entryways, Interior Decoration

Exterior Uses

As Building Stone, As Facing Stone, Garden Decoration, Office Buildings

As Building Stone, As Facing Stone, Garden Decoration

Other Architectural Uses

Curbing

Industry

Construction Industry

Arrowheads, Construction Aggregate, Cutting Tool, Spear Points

As Dimension Stone, Cement Manufacture, for Road Aggregate, Making natural cement

Medical Industry

Antiquity Uses

Artifacts, Monuments

Other Uses

Commercial Uses

Creating Artwork, Gemstone, In fire-starting tools, Jewelry, To ignite fire, Used in flintlock firearms

Creating Artwork, Gemstone

Types

Flint, Jasper, Radiolarite, Common Chert, Chalcedony, Agate, Onyx, Opal, Magadi-type Chert, Porcelanite, Siliceous Sinter

Cataclastic rock

Features

Clasts are smooth to touch, Easily splits into thin plates, Has High structural resistance against erosion and climate

Host Rock for Lead

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Present

Absent

Formation

Chert forms when microcrystals of silicon dioxide grow within soft sediments that become limestone or chalk. The chert formation can be either of chemical or biological origin.

Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Pseudotachylite is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.

Composition

Mineral Content

Quartz, Silicon

Iron Oxides, Pyroxene, Quartz, Stishovite, Sulfides

Compound Content

Silicon Dioxide

Carbon Dioxide, Silicon Dioxide, Sulfur Dioxide, Sulphur

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Weathering

✔ ✘

Types of Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion

Properties

Physical Properties

Hardness

6.5-77

1 7

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Grain Size

Very fine-grained

Fracture

Uneven, Splintery or Conchoidal

Uneven

Streak

White

Light to dark brown

Porosity

Highly Porous

Less Porous

Luster

Waxy and Dull

Vitreous

Compressive Strength

450.00 N/mm²60.00 N/mm²

0.15 450

👆🏻

Cleavage

Toughness

1.5

Specific Gravity

2.5-2.82.46-2.86

0 8.4

👆🏻

Transparency

Translucent to Opaque

Transparent to Translucent

Density

2.7 g/cm³2.7-2.9 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.74 kJ/Kg K0.92 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant

Heat Resistant

Reserves

Deposits in Eastern Continents

Asia

China, India, Iran, Japan, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam

South Korea

Africa

Kenya, Morocco, South Africa, Tanzania

Western Africa

Europe

Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom

Great Britain, Switzerland

Others

Greenland, Mid-Atlantic Ridge

Deposits in Western Continents

North America

Canada, Mexico, USA

South America

Bolivia, Brazil

Deposits in Oceania Continent

Australia

New South Wales, Queensland, South Australia, Western Australia

Central Australia, Western Australia

All about Chert and Pseudotachylite Properties

Know all about Chert and Pseudotachylite properties here. All properties of rocks are important as they define the type of rock and its application. Chert belongs to Sedimentary Rocks while Pseudotachylite belongs to Metamorphic Rocks.Texture of Chert is Banded, Rough whereas that of Pseudotachylite is Quench. Chert appears Glassy or Pearly and Pseudotachylite appears Dull and Soft. The luster of Chert is waxy and dull while that of Pseudotachylite is vitreous. Chert is available in black, brown, green, grey, red, white colors whereas Pseudotachylite is available in black, brown, green, grey, pink, white colors. The commercial uses of Chert and Pseudotachylite are creating artwork, gemstone, in fire-starting tools, jewelry, to ignite fire, used in flintlock firearms.